This month, Claus Futtrup writes about Compliance Alteration. This is a new follow-up article for the "Computation of Bass Reflex Alignments" article series that has been published monthly in Voice Coil since the May 2024 issue, and which is an expansion of the original article on Loudspeaker Bass Reflex Alignments originally published in audioXpress, January 2024. After discussing computation of discrete alignments such as B4, BL4, LR4, IB4, and CD4, this new article explores the real-world situation where it becomes impossible to have a system design that exactly matches a certain driver Qt, normally described as an alignment error (or misalignment).In this new article, Futtrup propose the advisable approach to extend the desired discrete target alignment to a broader range of driver Qt values. This was predicted and studied by Neville Thiele, Richard Small, and D. B. Keele from different perspectives, which this new article finally condenses and summarizes. As Futtrup explains, the "Compliance Alteration" technique deals with any discrete alignment but is also feasible in general to compensate for expected changes in suspension stiffness over time for any other alignment and is applied here to allow designers to modify tuning toward a desired target response function.
Next up, Mike Klasco and Nora Wong (Menlo Scientific) offer a new updated directory of Integrated Electronics for Loudspeakers for 2024. This extensive commented listing features suppliers and vendors for amplifier modules, DSP, and solutions for powered speakers, from the perspective of OEM, ODM, and contract manufacturers. A valuable resource.
And this month, James Croft (Croft Acoustical) returns to Voice Coil with an always enlightening patent review. The focus is an unpretentiously titled "Loudspeaker" patent, granted to industry veteran Michael Levy as the sole inventor. Many audioXpress and Voice Coil readers will recognize Levy from his brand Alta Audio and its XTL Transmission Line technology that applies the cabinet’s internal geometry to tune the frequency response using a hybrid approach. Basically, a ported enclosure design that Michael Levy says greatly increases power handling, lowers distortion, and extends bass frequencies.
For many loudspeaker designers, the fact that this patent was granted has been cause for consternation, but the reality, as James Croft details in his article, reveals that there's a lot that deserves attention. In this review, Croft looks at all the numerous examples of related inventions and prior art, which help explain why the submitted patent was found to have merit. An invention that, although seemingly familiar, now deserves more comprehensive testing.
And for this month's Test Bench, Vance Dickason focuses solely on the eagerly awaited Purifi Audio PTT10.0X04-NAB-01 10" Midbass Woofer. This is the latest driver from the famous Danish company, and the sixth Purifi woofer to be examined in Test Bench. This 4Ω woofer features extensive proprietary technology that includes the constant Sd surround, cone edge stiffening ring, and low magnetic hysteresis motor design. The PTT10.0X04-NAB-01 features a black anodized aluminum cone complemented by a 3.5" convex and slightly “pointed” dust cap of the same material, and a V-shaped fiber edge reinforcing ring glued around the outside rim of the back side of the cone. Compliance is provided by the unique NBR surround, which is now starting to be recognized in the industry for its unique concept and recognized benefits.
The Purifi PTT10.0X04-NAB-01 woofer also features a stacked pair of FEA-optimized ferrite ring magnets with milled and tapered plates, plus a neodymium pole magnet sandwiched between steel sections that serves to linearize the Bl. Driving the 10" cone assembly is a 2" diameter four-layer voice coil, wound with round aluminum wire on a non-conducting fiberglass former. Like the surround, this four-layer coil also exhibits some unique engineering, with two- and four-layer sections alternating on the length of the coil with varying widths. Two very thick copper shorting rings surround the coil within its full linear stroke, avoiding another potential source of distortion.
The October 2024 issue of Voice Coil closes with a dose of diverse Industry Watch stories, including the recent release of the latest FINEcone 2024 simulation software update by Loudsoft, now featuring a valuable Shape Optimizer.
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